The present disclosure relates to a hydraulic control apparatus for a transmission that allows selective engagement of at least one of a plurality of hydraulic pressure engaging elements to establish a plurality of shift stages and is equipped in a vehicle.
In the related art, this type of hydraulic control apparatus including first, second, third, and fourth normally closed linear solenoid valves, a clutch control valve that allows a D-range oil passage to communicate with any one of a low-speed stage oil passage and a high-speed stage oil passage, and a sequence valve that connects the first linear solenoid valve to a C1 clutch, connects the second linear solenoid valve to a C2 clutch, and the fourth linear solenoid valve to a B3 brake is known (for example, Japanese Patent Application Publication No. 2005-265101). The clutch control valve of the hydraulic control apparatus is controlled by a hydraulic pressure from the first linear solenoid valve that is supplied to an SL1 port, a hydraulic pressure from the second linear solenoid valve that is supplied to an SL2 port, a hydraulic pressure that is supplied to a port which communicates with the high-speed stage oil passage, and a spring. In addition, the sequence valve is controlled by a throttle pressure that is supplied to an SLT port, a solenoid modulator pressure that is supplied to a modulator port, a hydraulic pressure from the first or second linear solenoid valve that is supplied to an SL port, and a spring. In a case where an electrical failure occurs, the sequence valve selectively connects the D-range oil passage to one of the C1 clutch and the C2 clutch via the low-speed stage oil passage or the high-speed stage oil passage according to a state of the clutch control valve and connects the D-range oil passage to the B3 brake. In this manner, two shift stages having different transmission gear ratios from each other can be established according to the hydraulic control apparatus even when an electrical failure occurs during the drive of the vehicle.